0x22: 32 ch A/D and 8 ch D/A converter Raspberry Pi interface

 

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Background

The Raspberry Pi singleboard computer is becoming a popular platform for code development as well  playing an integrated part in sophisticated DIY projects. Hence, there is a desire to interface readily available sensors and actuators that can form the bridge from the software platform to the physical World.

Function

This design features the popular PCF8591 8 bit 4 ch A/D and 1 ch D/A converter and the DS3231 realtime clock. In essence this board is a 32 ch voltmeter and an 8 ch voltage source and forms an important step in any analogue data acquisition system or control loop. Using, for instance, the wiringPi library, a self-contained supervisory control and data acquisition (SCADA) system can easily be developed with this circuit board. Graphical user interfaces can be created using Qt and wiringPi. See the download section on this page for some example source code.

License terms
The 0x22 design is published under the Creative Commons Unported 3.0 License.  I do not profit from this design, neither should you. You are welcome to adapt, modify, and redistribute this design as long as the license terms are respected.

Physical size of PCB

100 mm (width) by 100 mm (height). Double-sided.

Rendering and photos

DipTrace 3D rendering, frontside with components

 

DipTrace 3D rendering, frontside, tilted, with components

 

DipTrace 3D rendering, backside with components 

 

0x22 module connected to a Pi Top 2 via the 0x31 IDC board

 

Screen dump of Qt interface running on the Pi Top 2 (Polaris). Loopback from DAC to ADC

 

Bill of materials

64 pcs. voltage divider resistor, 10k, 1206

1 pcs. diode bridge, DF10S

4 pcs. pullup resistor for I2C, 1206

1 pcs. pullup resistor for EEPROM WP, 1k, 1206

1 pcs. 1k LED current limiting resistor, 1206

1 pcs. 1 bit DIP switch, 2.54 mm pitch

17 pcs. decoupling capacitor, ceramic, 100 nF, 1206

8 pcs. 10 uF tantalum capacitor, 35 V, SMD

8 pcs. PCF8591 A/D D/A converter, wide SOIC-16

1 pcs. MCP1525 precision voltage reference, SOT-23

1 pcs. AMS1117-3V3, voltage regulator, SOT-223

1 pcs. CAT24C32 EEPROM, SOIC-08

1 pcs. DS3231 realtime clock with integrated TCXO, wide SOIC-16

1 pcs. 3-way male header, 2.54 pitch

2 pcs. 2-way male header, 2.54 pitch

3 pcs. 4-way male header, 2.54 mm pitch

1 pcs. 2×8-way male header, 2.54 mm pitch

2 pcs. jumper, pitch 2.54

1 pcs. 2-way terminal block, 5.08 mm pitch

1 pcs. barrel jack, 2.1 mm pin, 5.5 mm barrel

1 pcs. 40-way IDC connector, 2.54 mm pitch

1 pcs. LED, green, 1206

1 pcs. CR1220 button cell battery holder

1 pcs. CR 1220 button cell battery

 

Estimated cost

Components, connectors,  and the circuit board should not cost more than EUR 20,-.

 

Downloads

DipTrace v. 3 schematic file: 0x22rev1_schematic

DipTrace v. 3 PCB design file: 0x22rev1_ratlined_public

Gerber files: 0x22rev1_Gerber

Qt 5 GUI source code: QtGUI_0x22

 

Links

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